It all commences at the start of the takeoff roll with the starting vortex. PPRuNe's resident aerodynamicist, Owain Glyndwr, has numerous words to say on circulation which is the buzzword you seek. Our other aerody guru, djpil, likewise, may have some comments on the topic as well.
Also have a read of Gentry's articles at
Gentry Sailing | Theory and Practice
You might, in particular, have a read of Gentry's Origins of Lift at
http://www.gentrysailing.com/pdf-the...ns-of-Lift.pdf